cloud-fan commented on a change in pull request #26182: [SPARK-29523][SQL] SHOW
COLUMNS should do multi-catalog resolution.
URL: https://github.com/apache/spark/pull/26182#discussion_r339900738
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File path:
sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/parser/AstBuilder.scala
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@@ -2911,4 +2911,28 @@ class AstBuilder(conf: SQLConf) extends
SqlBaseBaseVisitor[AnyRef] with Logging
override def visitRefreshTable(ctx: RefreshTableContext): LogicalPlan =
withOrigin(ctx) {
RefreshTableStatement(visitMultipartIdentifier(ctx.multipartIdentifier()))
}
+
+ /**
+ * A command for users to list the column names for a table.
+ * This function creates a [[ShowColumnsStatement]] logical plan.
+ *
+ * The syntax of using this command in SQL is:
+ * {{{
+ * SHOW COLUMNS (FROM | IN) tableName=multipartIdentifier
+ * ((FROM | IN) namespace=multipartIdentifier)?
+ * }}}
+ */
+ override def visitShowColumns(ctx: ShowColumnsContext): LogicalPlan =
withOrigin(ctx) {
+ import org.apache.spark.sql.connector.catalog.CatalogV2Implicits._
+
+ val table = visitMultipartIdentifier(ctx.table)
+ val namespace = Option(ctx.namespace).map(visitMultipartIdentifier)
+ if (namespace.isDefined && namespace.get.length > 1 && table.length > 1) {
Review comment:
Since we don't have v2 SHOW COLUMNS yet, so in `ResolveSessionCatalog`, we
should simply check that
1. the table name has <= 2 parts
2. the namespace name should have only one part if specified
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